A device of this kind, also called a “pendulum oscillator” or “pendulum,” is intended in particular to be part of a transmission of a motor vehicle.
In a motor vehicle transmission, at least one torsion damping system is usually combined with a clutch capable of selectively connecting the engine to the gearbox.
A combustion engine exhibits irregularities due to the successive combustion events in the engine's cylinders, said irregularities varying in particular depending on the number of cylinders.
The damping system conventionally has springs and friction elements whose function is to filter vibrations due to rotational irregularities of the engine, and takes effect before engine torque is transmitted to the gearbox. This allows such vibrations to be prevented from entering the gearbox and causing shocks, noise, and undesirable acoustic impacts therein.
In order to improve filtration further, it is known to use a pendulum-type damping device in addition to the usual damping device.
The Applicant's patent application FR 2981714 discloses a pendulum-type damping device having an annular support intended to be rotationally driven around its axis, and pendulum masses mounted on the outer periphery of the support. Each mass has a pendulum motion imparted to it during operation, and has two parts mounted axially on either side of the support and connected by two spacers each spanning an opening of the support. A roller is mounted between a rolling track configured in each spacer and the edge of the corresponding opening of the support.
In reaction to rotational irregularities, each mass shifts so that its center of mass oscillates in pendulum fashion. The oscillation frequency of each mass is proportional to the rotation speed of the driving shaft; the corresponding multiple can assume, for example, a value close to the predominant harmonic order of the vibrations responsible for strong rotational inconsistencies at close to idle speed.
The spacers are fastened to the two parts of the mass by riveting. The heads of the rivets abut against the outer radial faces of the parts of the mass, i.e. against the faces opposite to the annular support, and thus protrude axially from said parts of the mass. The volume thereby swept out during operation is relatively large, so that surrounding parts need to be dimensioned accordingly.
The load-bearing section of the rivet is essentially weaker than the total cross section of the part to be connected, thus weaker than the force-fitted spacer. The shapes of the spacer are simpler and thus easier to manufacture.